In general, elevator cars in a machine roomless configuration are driven vertically through a hoistway by an electric motor and one or more elevator brakes that are supported by a bedplate and positioned within an upper portion of the hoistway. In alternative configurations, the electric motor and the associated brakes may be provided within a separate machine room rather than within the hoistway. Operation of the motor rotates an output shaft as well as a traction sheave coupled thereto. Tensile members, such as belts, ropes, cables, and the like, connecting the elevator car to a counterweight are at least partially fitted about the traction sheave. As the motor rotates the traction sheave, the tensile members are caused to travel around the traction sheave, and thus, lift or lower the elevator car within the hoistway to a desired floor or landing.
The motor of a typical elevator system is used to slow the elevator car as the car approaches a desired landing while one or more elevator brakes are used to hold the car at the landing as passengers load or unload the car. Elevators may also employ emergency brakes configured to automatically engage in the event of a malfunction, a power outage, or any other emergency situation. Elevator brakes may mechanically and/or frictionally engage a rotor, a drum, or the like, so as to resist rotation of the output shaft and the traction sheave and to prevent further travel of the elevator car. The capacity of the elevator brake to sufficiently slow and hold a moving elevator car may be gauged by its brake torque.
The brake torque of an elevator brake may be sufficiently rated according to the particular design or application of the elevator, the specifications of the elevator drive system, and other considerations. The brake torque of an elevator brake must additionally be sufficiently rated to produce the minimum level of torque required by regional and/or universal safety codes and regulations. Due to the mechanical nature of elevator brakes, however, the braking capacity or brake torque supplied by an elevator brake may change with time. The brake torque may decrease due to several factors. For example, the coefficient of friction between the brake and the rotor or drum may decrease due to oxidation, moisture, and the like. The normal forces of springs or dampers in elevator brakes used to exert friction may also decrease due to natural relaxation. Furthermore, misalignments and/or malfunctions may occur over time, causing the brake to drag and reducing overall braking capacity.
Currently, the health condition of elevator brakes is manually and periodically inspected by maintenance service personnel. Based on the results of the inspection, brakes may be repaired/replaced or disregarded until at least the next inspection due. While regularly conducted maintenance may serve as an adequate safety measure, current inspection techniques lack a more efficient way to quantify the braking capacity of a brake and to track the braking capacity over time. Furthermore,
Furthermore, with the increasing number of machine roomless elevator installations, in which the elevator brakes are positioned within the hoistway rather than in a separate machine room, it is becoming even more difficult to safely access and inspect elevator brakes on a regular basis.